The present invention relates to low pressure ceramic filter systems for liquid and more particularly to a low pressure beer filter system including a novel filter supporter which causes essentially even liquid flow through all parts of a ceramic filter.
There are several objective performance criteria by which to assess the value of a liquid filter system. One of the most important criteria is the speed with which a filter system can filter a representative liquid volume, speed being closely associated with filter efficiency. In order to expedite a filtering process, it is always desirable to design filters which have a large filter area and wherein the entire filter area is continually used during the filtering process.
One advantageous filter type includes a ceramic filter medium which is capable of removing extremely fine particles from a liquid. Ceramic filters are particularly advantageous in the beer industry where filters must be able to remove micro-bacteria and other fine particulates. Referring to FIG. 1, a typical ceramic filter system 8 includes a spindle 10 on which is mounted a cylindrical ceramic filter 12. Spindle 10 includes a solid bar 14 on the bottom of which extends an inverted cup member 16. An annular flange 18 extends radially outwardly from cup member 16. One or more (preferably three) large outlets 20 are provided in an upper portion of member 16 above flange 18. Filter 12 has upper upper 12b and lower 12a sections and rests on an upper surface of flange 18. A gasket (not shown) is provided between filter 12 and flange 18 so that liquid cannot pass therebetween. A sealing gasket 22 is provided at the top of filter 12. Thus, spindle 10 and filter 12 form a chamber 24 therebetween having outlet 20.
In operation, system 8 is placed inside a large vat of low pressure beer. Once chamber 24 is filled, as beer exits outlet 20, a "beer vacuum" occurs therein and an equal amount of beer is drawn through filter 12 into chamber 24.
One problem with system 8 has been uneven and therefore inefficient liquid flow through filter 12. Specifically, a greater relative flow passes through lower section 12a than through upper section 12b.
With chamber 24 filled, as beer exits outlet 20, the beer vacuum is primarily adjacent outlet 20 and lower filter section 12a. Thus, while some beer passing through outlet 20 is drawn from upper section 12b, a greater relative percentage per unit length is drawn from lower section 12a. Even as lower section 12a becomes clogged, because the vacuum is adjacent section 12a, the vacuum still draws an inordinate amount of beer through section 12a. Using clogged section 12a instead of section 12b is inefficient.
One filter flow spreading solution is to provide a pipe-like spindle which forms a plurality of outlets along its length. One such design, albeit used to filter high pressure liquid, is described in U.S. Pat. No. 600,651 which issued on Mar. 15, 1898. That design includes a pipe-like spindle which forms a plurality of apertures evenly distributed along its length. The high pressure causes fluid flow through all sections of the filter and through all spindle apertures.
Unfortunately, while this solution generates even flow in a high pressure environment, it has been found that this solution only generates an insubstantial amount of additional flow through the upper portion of a filter in a low pressure environment. As with the typical filter system described above which forms only a single outlet, it is believed that the flow characteristics observed at low pressure where there are a plurality of apertures result from the beer vacuum being concentrated at the lower end of the spindle adjacent the lower most apertures. In this case there is relatively greater flow through the lower apertures than through the upper apertures.
Therefore, it would be advantageous to have a filter system for removing impurities from low pressure liquid wherein the system causes essentially even flow through all filter sections thereby increasing filter flow rate.